1. Field of the Invention
The present invention relates to a radiation image capturing system having a radiation conversion panel for detecting a radiation that has passed through a subject and converting the detected radiation into radiation image information.
2. Description of the Related Art
In the medical field, there have widely been used radiation image capturing apparatus which apply a radiation to a subject and guide the radiation that has passed through the subject to a radiation conversion panel, which captures a radiation image from the radiation. Known forms of the radiation conversion panel include a conventional radiation film for recording a radiation image by way of exposure, and a stimulable phosphor panel for storing radiation energy representing a radiation image in a phosphor and reproducing the radiation image as stimulated light by applying stimulating light to the phosphor. The radiation film with the recorded radiation image is supplied to a developing device to develop the radiation image, or the stimulable phosphor panel is supplied to a reading device in order to read the radiation image as a visible image.
In an operating room or the like, it is necessary to read a recorded radiation image immediately from the radiation conversion panel after the radiation image has been captured, for the purpose of quickly and appropriately treating the patient. As a radiation conversion panel that meets such a requirement, there has been developed a radiation detector having a solid-state detector for converting radiation directly into electric signals, or for converting radiation into visible light with a scintillator and then converting the visible light into electric signals, so as to read the detected radiation image.
In a radiation image capturing system which employs a radiation detecting cassette housing a radiation conversion panel therein, for accurately capturing a radiation image, the capturing of the radiation image is preceded by the transmission of image capturing conditions for an area to be imaged from the radiation detecting cassette through a communication cable (see Japanese Laid-Open Patent Publication No. 2003-172783) or the positioning of the radiation source and the radiation detecting cassette with respect to each other (see Japanese Laid-Open Patent Publication No. 2006-305105 and Japanese Laid-Open Patent Publication No. 2007-020679).
According to Japanese Laid-Open Patent Publication No. 2003-172783, though a radiation source can recognize the area of a subject (patient) to be imaged from the image capturing conditions transmitted from the radiation detecting cassette, the radiation source is unable to determine whether the distance between the radiation source and the radiation detecting cassette matches a predetermined distance (source-to-image distance, hereinafter also referred to as “SID”) from the radiation source to the radiation detecting cassette at the time a radiation image of the subject is to be captured. Therefore, if the radiation image is captured when the distance between the radiation source and the radiation detecting cassette does not match the SID, then highly accurate radiation image information cannot be produced.
According to Japanese Laid-Open Patent Publication No. 2006-305105 and Japanese Laid-Open Patent Publication No. 2007-020679, a surgeon or a radiological technician visually checks if the distance between the radiation source and the radiation detecting cassette matches the SID or not by seeing the graduations on a measure mounted on the radiation source, after which the surgeon or the radiological technician manually position the radiation source and the radiation detecting cassette with respect to each other to equalize the distance between the radiation source and the radiation detecting cassette with the SID. Though the patient needs to be treated quickly and adequately, the visual checking and the manual positioning procedure tends to pose an undue burden on the surgeon or the radiological technician, who may possibly fail to capture a radiation image of the patient efficiently.